Heat treating apparatus utilizing nuclear energy



R, SCHULTEN 3,293,138

HEAT TREATING APPARATUS UTILIZING NUCLEAR ENERGY Dec. 20, 1966 2Sheets-Sheet 1 Original Filed March 23. 1960 Dec. 20, 1966 R. SCHULTEN3,293,138

HEAT TREATING APPARATUS UTILIZING NUCLEAR ENERGY Original Filed March23, 1960 2 Sheets-Sheet 2 SUBSTANCE 2O ueumou ABSORBING 5% iii fra (W KQ (Q United States Patent 3,293,138 HEAT TREATENG APPARATUS UTILIZINGNUCLEAR ENERGY Rudolf Schnlten, Lutzeisachsen an der Bergstrasse, amoberen Klingenherg, Germany, assignor to Brown, Boveri 8: CieAktiengeselischaft, Mannheim, Germany, a corporation of Germany Originalapplication Mar. 23, 1960, Ser. No. 16,979, new Patent No. 3,181,99,dated May 4, 1965. Divided and this application Jan. 3, 1964, Ser. No.335,479 Claims priority, application Germany, Mar. 24, 1959, R 52,589 10Ciaims. (Cl. l7639) This application is a division of my copendingapplication, Serial No. 16,979, filed March 23, 1960, now Patent No.3,181,999 granted May 4, 1965.

My invention rel-ates to industrial production methods and means whichutilize nuclear-fission energy for the heat processing of materials,such as for melting purposes or performing chemical reactions to producecalcium carbide, phosphorous or other substances, for example.

in the industrial utilization of nuclear-fission energy in nuclearreactors as heretofore known, the evolving reaction energy is impartedas heat to a circulating liquid or gaseous coolant which conveys theheat out of the reaction zone to an extraneous location, for example toa heat exchanger, where the heat is applied to a secondary fluidcirculation system. The insertion of the primary coolant circulationserves to prevent radioactivity from being conveyed out of the reactorby the operating medium proper. However, the inserted primary coolantcirculation system makes it infeasible to efiiciently use a nuclearreactor for physical and chemical reactions that merely require heatprocessing of the reaction material, particularly at high temperatures.For that reason, the known nuclear reactors have heretofore not beenused for such industrial purposes, especially in view of the fact thatthe zone to be heated by the cooling medium always has a considerablylower temperature than obtaining in the reaction zone of the nuclearreactor core.

It is an object of my invention to provide a method and means for theheat processing of substances in order to perform physical or chemicalreactions with the aid of nuclear-fission energy, which affords keepingthe technological expenditure within extremely low limits and thus issuitable for production purposes in industry.

To this end, and in accordance with a feature of my invention, themoderator block of a nuclear reactor, preferably the graphite blockstructure of a thermal-neutron reactor, is operated without a coolantcirculation system but is provided, aside from the bores for the nuclearfuel elements, with a number of additional bores for the rece tion ofthe substances to be heat-processed, so that the moderator structuredirectly constitutes the source or storage of the heat active in theprocessing bores of the moderator structure to perform the desiredphysical or chemical reaction.

It has been found that various reactions can thus be carried outdirectly in the reactor core despite the radioactivity obtaining in thecore, and that by shutting down the nuclear reaction for the duration ofthe heat processing of the reaction material, any radioactivecontamination of the reaction material can be kept within permissiblelow limits.

Due to the fact that the only cooling effect upon the core is caused bythe material being heat processed, the conventional circulating coolantbeing absent, the high temperature in the reaction zone can be directlyutilized with a minimum of losses and without the need for theconsiderable expenditures in equipment and space required for thecirculation of a coolant through the core.

In other respects a reactor for the purposes of the invention maycorrespond to the types of reactors known for electric power productionor research purposes. The reactor is operated with high-temperatureresistant nuclear fuel elements such as available in the form of rods orpellets of enriched uranium.

The above-mentioned objects, advantages and features of my invention,said features being set forth with particularity in the claims annexedhereto, will be apparent from, and will be mentioned in, the followingwith reference to the embodiment of a heat processing nuclear reactoraccording to the invention illustrated by way of example on theaccompanying drawings, in which:

FIG. 1 is a vertical, sectional view of the reactor,

FIG. 2 a horizontal cross section through the core zone of the reactor,and

FIG. 3 shows in cross section an enlarged detail of a portion of FIG. 1corresponding to that located at the upper left-hand side of themoderator structure of FIG. 1.

The reaction zone of the illustrated nuclear reactor is filled with amatrix structure 1 of graphite which may conventionally comprisehorizontal layers each composed of prismatic blocks or columns ofgraphite. As will be more fully described, the core structure 1 isprovided with nuclear fuel channels and with channels for introductionof the material to be heat processed. The reactor is primarily used anddesigned as a heat generator or furnace. For that reason, coolingchannels and a system for circulating a gaseous or liquid coolantthrough the core are not present or are not needed for normal operationand hence are not shown on the drawing.

The heat processing is effected by directly utilizing the heat producedby nuclear fission and stored in the graphite core structure 1. Thereare several ways of proceeding in this manner. One way is to remove,during heat processing, the nuclear fuel elements from the fuel channelsof the graphite structure 1 and to fill the reaction material to beprocessed into additional core channels provided for this purpose.Another way is to leave the fuel elements in operative position Withintheir respective channels while the material is being heat processed inthe processing channels. In the latter case the heat processing iseffected not only by the heat previously stored in the graphite corestructure but also by heat continued to be produced by nuclear fission,the reactor being permitted to continue operating under criticalconditions. However the nuclear reaction may also be shut down duringheat processing by introducing absorber sleeves or rods into the core. Acontinued critical operation of the nuclear reactor during heatprocessing is applicable in cases where such continued operation doesnot result in objectionable conditions relative to the reaction product.Such objectionable conditions are encountered, for example, if anincreased or excessive induced radioactivity of the product is incurreddue to the continuing neutron flux. As a rule, it is preferable toperform the heat processing by direct heat exchange with the reactorcore while the nuclear activity of the fuel elements is shut down.

A particularly favorable Way of performing the method of the inventionis for the purpose of chemical endothermic reactions such as exemplifiedby the production of calcium carbide more fully described hereinafter.Such an endothermic reaction can be performed by first running thenuclear reactor critical under heat-retaining conditions of themoderating reactor core, i.e. without the use of any coolant circulationpassing through the core zone. After the desired high temperature of thecore is reached, the processing material is introduced in such aquantity as to act substantially as the only coolant with the effect ofshutting down the critical reactor operation without necessity ofremoving the fuel elements.

Upon completion of the heat processing, the reactor is returned tocritical operation simply by removing the processed material prior tointroducing a new quantity.

A particularly favorable design of the reactor core suitable for themodes of operation described above is obtained by providing the graphitestructure 1 with at least two groups of channels extending perpendicularto each other and preferably having a circular cross section of theindividual channels. One group of these channels serves for receivingthe fuel elements 2', and at least one of the other groups for receivingthe reaction material to be heated. In the illustrated embodiment, thechannels for the fuel elements are constituted by horizontal bores 2,and the channels for the reaction material by vertical bores 3. Suchvertical processing channels are preferable because they permitintroducing and discharging the reaction material by gravity, whereasthe utilization of gravity effects is less significant relative to thenuclear fuel elements.

The vertical bores 3 are lined with tubes 4 of graphite or berylliumoxide which are' preferably used as hightemperature resistant andneutron-moderating substances. The tubes 4 may also be lined with otherhigh-temperature resistant materials known for such purposes andpreferably available as nitrides, carbides, silicides or oxides. Thelining also serves for protecting the moderator substance, in thepresent case the graphite, from the fission products. The tubes 4 areextended into a free plenum space 5 above the core zone in order tofacilitate introducing the reaction material into the tube entrances,and the upper ends of the tubes 4 are provided with funnel-shapedenlargements 6. Instead of thus extending the tubes 4 into the upperplenum space 5, separate guiding tubes may be coaxially attached to theupper ends of the respective bores 3. If desired, similar guiding tubes,extensions, or funnel portions may be provided for the horizontal fuelbores 2.

The core is enclosed by a reflector 7 which in turn is enclosed by ashield 8. The core space within reflector and shield is covered at thetop by a steel plate 11 to which the tubes 4 are fastened. The shield 8consists conventionally of a mass of graphite dust or graphite granulesor the like and serves to shield the environment from the heat as wellas the radioactivity of the core zone. For shielding from radioactivity,it is preferable to add substances absorptive to neutrons and gammaradiation, such as boron, boron carbide, iron-barite or the like.

The shield 8 is enclosed within a jacket 9 of sheet steel which forms anadditional shield for absorption of gamma rays. Semi-tubes 10 are weldedonto the outer peripheral surface of the jacket 9 and, during operation,are traversed by a liquid or gaseous coolant for dissipating the heatpenetrating to the outside of the processing structure proper. It willbe understood that this coolant system, located externally of the corezone proper, is to be distinguished from the primary coolant circulationsystern which in the known reactors passes through the fuel channels orthrough other channels directly in the interior of the moderator corefor conveying the developed heat to the outside of the reactor. Incontrast thereto, the system of cooling tubes 10 is heat-insulated fromthe interior of the core and from the fuel elements and essentiallyconstitutes an external protective device.

The above-described components are mounted within an external shieldstructure 18 of concrete. The reaction material to be processed issupplied through an opening 26 in the top portion of the concrete shield18 and enters into the plenum chamber 5 in which a feeder device forpassing the reaction material into the tubes 4 is located. The feederdevice comprises a number of downwardly open tubes 19 mounted on abridge 20. The tubes 19 are made of a high-temperature resistantmaterial such as beryllium oxide (BeO or graphite. The material may alsocontain an addition of neutron-absorbing substance such as boron,cadmium or hafnium, or the tubes may be lined with such substance, inorder to interrupt the nuclear chain reaction during the chemical orphysical heat processing of the material, thus preventing the reactionmaterial from becoming activated by photoneutrons.

The bridge 20 is mounted on four screw spindles 21 which are uniformlydistributed over the periphery and can be rotated to thereby lower orlift the bridge 20. For this purpose, the bridge 20 is provided withfour nuts 22 in threaded engagement with the spindles 21 (FIG. 3). Thespindles are journalled in bearings 23 and 24. They are driven by meansof respective pinions 25. However the drive may also be effected bymeans of an endless chain mechanically interconnecting all four spindles21, or the driving motion may be directly imparted to the spindles byrespective gears or motors. In lieu of such a spindle drive, the tubes19 or corresponding cylindrical feeder structures may also be displacedin parallel motion by synchronously controlled hydraulic pistons or anyother suitable drive known for related nuclear-reactor purposes.

The filling of the reaction material onto the bridge 21 is effected inknown manner through the opening 26, for example with the aid of amaterial-distributing spider, if necessary. The best suitable manner andmeans for thus feeding the processing material into the processingchannels depends upon the particular form in which the material is beingused, for example in form of granules or rods.

The processed material is discharged through tubes 12 which likewiseconsists of a high-temperature resistant material such as graphite, BeOor alloy steel suitable for such purposes. The tubes 12 are locatedinside the shield 8 and are fastened to .a closure plate 15 of steel.Disposed between each two aligned tubes 4 and 12 is a closure 13 with adrive 14. The closure 13 consists of a planar plate located directlybeneath the reflector. The plate 13 has bores of the same diameter anddistribution as the tubes 12. The drive 14 consists of a spur gear whichengages rack teeth (not shown) of the'closure plate 13 for shifting itbetween open and closed positions. In closed position, the bores ofplate 13 are located beside the respective tubes 12. For discharging thereaction material from the core zone, the drive 14 shifts the plate sothat the bores in plate 13 register with the respective tubes 12. Thereaction material then drains from the channels 3 through the tubes 12and through a funnel 16 into a transporting vessel or onto a suitableconveyor.

The horizontal bores, like the bores 3, are lined with tubes andprovided with flanges and stub pipes 17. The stubs 17 serve forconnection to a fuel exchanging device of known type (not illustrated).

The particular embodiment of the heat-processing reactor according tothe invention shown on the drawings is particularly designed foroperating in such a manner that first the graphite structure 1 is heatedup by nuclear-fission energy, and that thereafter the chain reaction isshut down by running the feeder tubes 19 into the reaction zone wherebythe reaction material is protected from induced activity .and the heatprocessing is carried out by means of the heat energy stored in thegraphite core structure. This method is particularly advantageous foruse with reaction substances from which otherwise a higher inducedactivity due to photoneutrons is to be expected.

For other physical or chemical processing, a shut-down of the chainreaction may not be necessary. In such a case the reactor structure canbe simplified considerably. The feeder device can then be omitted andthe processing material can directly be entered into the correspondingbores of the graphite core structure. The entire processing operationmay also be performed continuously. The conditions for continuousoperation follow from the reaction equation and the required dwellingperiod of the reaction material in the reactor. That is, when thethroughput period of the reaction material passing through the reactoris equal to or smaller than the required dwelling period, the plant issuitable for continuous operation.

The plenum chamber above the graphite core structure which, in theillustrated reactor embodiments, contains the feeder device, may alsoserve as a pro-heating chamber.

When operating the heat-processing reactor intermittently, i.e. whenalternately inserting the fuel elements for heating-up of the core zoneand thereafter introducing the reaction material for consuming thestored heat, the reactor may also be used in tandem operation with asecond reactor of the same type or design. If desired, only one set offuel elements is then required which is inserted, each time for a givenperiod of time, into one of the respective reactors while the otherreactor is being supplied with the reaction material. Upon terminationof the processing period, the operations of these two reactors areexchanged relative to each other.

The reactor according to the invention is advantageously applicable as amelting furnace or for performing corresponding chemical reactions suchas for producing calcium carbide or phosphorus. Such endothermicprocesses are particularly suitable to make the processing materialoperate as a coolant in the interior of the nuclear reactor zone thusreducing the nuclear activity or interrupting the chain reaction whilethe endothermic chemical reaction is in progress.

The operation of such a melting furnace reactor will he furtherdescribed with reference to specific examples.

The production of calcium carbide (CaC is in accordance with thereaction equation This reaction is endothermic and consumes 112 kcal.for forming 1 mol=64 g. carbide. The operating temperature in thenuclear-reaction furnace is about 2200 C. Carbide formation takes placeunder atmospheric pressure at 1620" C. The industrial mass-productionfurnaces now being used have a power demand of approximately 25 rnw.(megawatt).

The reactor for the pnocessing example here being described is designedfor a production of 20,000 metrical tons (t) of CaC per annum. Thereactor operates with enriched uranium as fuel in which the ratio ofgraphite to uranium 235 is such that 1 g. U 235 is present forapproximately kg. graphite. The graphite mass of the reactor corestructure is approximately 100 t. Hence, the corresponding quantity of U235 is 10 kg.

According to the reaction equation, 1.75 -1i0 kcal. are required per kg.carbide. The graphite structure has a heat storing capacity of Q=O.5-10kcal./ C. This results in Q=2.5-10 kcal. for a temperature difference ofAt:500 C. Based upon these quantitative values the production rate isapproximately 14.3 t per charge.

The charge is filled into 200 bores (3 in FIG. 1) each having a diameterof 12 cm. The total volume of the bores is V=7 rn. corresponding to 15.4t CaC Since the heat exchange is effected by radiation, the radiatedheat quantity according to the Stefan-Boltzmann law is Q=5'10 kcal./h.=58 mw. for .a temperature of T=257 3 K. This 58 mw. reactor thereforeaffords producing approximately 15 t of CaC in 5.6 hours.

The production of phosphorus is in accordance with the reactionequation:

This reaction consumes 282 kcal. for producing 2 moles=62 g. ofphosphorus. The operating temperature is 1300 to l400 C.

Used for the performance of the process is the reactor of the design andrating mentioned above with reference to the production of calciumcarbide.

The heat quantity required for producing 1 kg. phosphorus is 4.5510kcal. With the heat storing capacity of the graphite core structuregiven above (0510 kcal./ C.) and the temperature difference of At=500C., the quantity of the phosphorus being produced is about 5.5 t percharge.

The quantities of phosphorite, quartz and coke corresponding to theforegoing reaction equation are inserted into the nuclear furnace ingranular form so that P and CO can readily draw off.

The resulting calcium silicate is drained from time to time in form of aliquid slag. The products P and CO evolving from the furnace in gaseousform are passed to a dust separator and subsequently cooled, wherebyyellow phosphorus is precipitated.

The carbon monoxide exhausted from the furnace is useful for the purposeof various syntheses by adding H A slag suitable for manufacture ofcement is obtained when using bauxite in lieu of quartz sand. Theferrophosphorus resulting as a by-product, due to the iron content ofthe mixture, is applicable for smelting purposes or can be used forproducing alkali phosphates by adding alkali substances.

The phosphorus obtained as a yellow precipitate can be subjected tofurther fabrication in accordance with conventional single-stage ortwo-stage methods.

The above-described nuclear-reactor furnace is also well applicable as amelting furnace for substances which have an extremely high meltingpoint and must be produced in hyper-pure form. For example, quartzglass, titanium, beryllium and the like substances, can be produced inthis manner.

While I prefer using for the purposes of the invention a thermal nuclearreactor as exemplified by the illustrated and above-describedembodiment, the heat processing according to the invention can also becarried out in a fast reactor in which case, on account of the geometricconditions, the chemical and physical production processes must beperformed within a blanket structure.

I claim:

1. A furnace for heating processing of material by means ofnuclear-fission energy, comprising a nuclear reactor having agraphite-moderated core structure, said core structure having two groupsof bores, nuclear fuel elements insertable into one of said groups ofbores for heating said core structure by nuclear chain reaction, andfeeder means comprising a plurality of movable guide members and meansfor inserting said guide members respectively into the bores of saidother group for feeding the material to be processed into said latterbores, said latter bores when containing said material constitutingsubstantially the only cooling means of said core structure duringfurnace operation.

2. In a nuclear furnace for heat processing of material according toclaim 1, said bores of one of said group extending through said corestructure at a right angle to the direction of said other bores.

3. In a nuclear furnace for heat processing of material according toclaim 1, said fuel-element bores extending horizontally and saidprocessing bores extending vertically through said core structure.

4. A furnace for heat processing of material by means of nuclear-fissionenergy, comprising a nuclear reactor having a graphite-moderated corestructure, said core structure having two groups of bores, nuclear fuelelements insertable into one of said groups of bores for heating saidcore structure by nuclear chain reaction, feeder means for placing thematerial to be processed into the bores of said other group, said feedermeans comprising a number of tubes for receiving said material, saidtubes being coaxially aligned with said latter bores respectively, andmeans for inserting said tubes into said respective latter bores, thecontents of said latter bores constituting substantially the onlycooling means of said core structure during furnace operation.

5. A furnace for heat processing of material by means of nuclear-fissionenergy, comprising a nuclear reactor having a graphite-moderated corestructure, said core structure having two groups of bores, nuclear fuelele ments insertable into one of said groups of bores for heating saidcore structure by nuclear chain reaction, feeder means for placing thematerial to be processed into the bores of said other group, said feedermeans comprising a number of tubes for receiving said material, saidtubes being coaxially aligned with said latter bores respectively, andmeans for inserting said tubes into said respective latter bores, thecontents of said latter bores constituting substantially the onlycooling means of said core structure during furnace operation, saidfeeder means comprising a supporting frame structure to which said tubesare fastened, and parallel motion guide means displaceably connectingsaid frame structure with said core structure, said means for insertingsaid tubes into said respective latter bores comprising drive means forshifting said frame structure toward and away from said core structurefor inserting and removing said tubes relative to said latter bores.

6. In a nuclear furnace according to claim 4, said tubes consisting ofrefractory material which comprises neutronabsorber substance in aquantity sufiicient to stop nuclear chain reaction in said corestructure when said tubes are inserted.

7. In a nuclear furnace according to claim 4, said tubes being ofberyllium oxide with a lining of neutron absorber substance formoderating the reaction during heat processing of said material.

3. A furnace for heat processing of material by means of nuclear-fissionenergy, comprising a nuclear reactor having a graphite-moderated corestructure, said core structure having two groups of bores, nuclear fuelelements insertable into one of said groups of bores for heating saidcore structure by nuclear chain reaction, feeder means for placing thematerial to be processed into the bores of said other group, said feedermeans comprising a number of guide tubes coaxially aligned with saidrespective bores of said other group, each of said guide tubes havingone end adjacent to one of said latter bores and having a widening,funnel-shaped other end, and said feeder means further comprising anassembly of displaceable tubes for containing the material to beprocessed, said displaceable tubes being coaxially aligned with saidrespective guide tubes, and means for moving said assem bly in adirection parallel to the alignment axes for inserting said displaceabletubes through said funnel-shaped ends and said guide tubes into saidbores of said other group.

9. A furnace for heat processing of material by means of nuclear-fissionenergy, comprising a nuclear reactor having a core structure ofgraphite, said core structure having a group of horizontal bores fornuclear fuel elements and having a group of vertical processing bores, ashielding structure enclosing said core and having a material inlet atthe top and an outlet at the bottom, said shielding structure forming aplenum chamber above said core structure, a feeder device mounted insaid plenum chamber and having distributor means for passing thematerial to be processed from said inlet into said respective processingbores, and a controllable closure device at the bottom of said corestructure for closing and opening said processing tubes relative to saidoutlet.

10. A furnace for heat processing of material by means ofnuclear-fission energy, comprising a nuclear reactor having a corestructure of graphite, said core structure having a group of horizontalbores for nuclear fuel elements and having a group of verticalprocessing bores, a shielding structure enclosing said core and having amaterial inlet at the top and an outlet at the bottom, said shieldingstructure forming a plenum chamber above said core structure, a feederdevice mounted in said plenum chamber and having distributor means forpassing the material to be processed from said inlet into saidrespective processing bores, and a controllable closure device at thebottom of said core structure for closing and opening said processingtubes relative to said outlet, said feeder device comprising a framestructure vertically displaceable in said plenum chamber relative tosaid core structure, a number of tubes secured to said frame structurein coaxial alignment With said respective processing bores andinsertable into said bores by lowering of said frame structure.

References Cited by the Examiner UNITED STATES PATENTS 2,812,304 11/1957Wheeler 176-44 2,910,416 10/1959 Daniels 17617 2,931,762 4/1960 Fermi17661 2,943,986 8/1960 Thorpe et al. 176-39 2,982,711 5/1961 Rand 176-312,983,658 5/1961 Hyman et al 176- 3O FOREIGN PATENTS 574,103 6/1959Belgium. 861,316 2/ 1961 Great Britain.

L. DEWAYNE RUTLEDGE, Primary Examiner.

LEON D. ROSDOL, Assistant Examiner.

1. A FURNACE FOR HEATING PROCESSING OF MATERIAL BY MEANS OFNUCLEAR-FISSION ENERGY, COMPRISING A NUCLEAR REACTOR HAVING AGRAPHITE-MODERATED CORE STRUCTURE, SAID CORE STRUCTURE HAVING TWO GROUPSOF BORES, NUCLEAR FUEL ELEMENTS INSERTABLE INTO ONE OF SAID GROUPS OFBORES FOR HEATING SAID CORE STRUCTURE BY NUCLEAR CHAIN REACTION, ANDFEEDER MEANS COMPRISING A PLURALITY OF MOVABLE GUIDE MEMBERS AND MEANSFOR INSERTING SAID GUIDE MEMBERS RESEPCTIVELY INTO THE BORES OF SAIDOTHER GROUP FOR FEEDING THE MATERIAL TO BE PROCESSED INTO SAID LATTERBORES, SAID LATTER BORES WHEN CONTAINING SAID MATERIAL CONSTITUTINGSUBSTANTIALLY THE ONLY COOLING MEANS OF SAID CORE STRUCTURE DURINGFURANCE OPERATION.